Successful waterborne acrylic (or latex emulsion) coating compositions must deliver performance comparable to traditional solvent-borne coatings, while meeting increasingly stringent VOC (volatile organic compounds) emission regulations. It is known in the coatings art that the formation of a latex film can be facilitated by incorporating a coalescing agent in the latex emulsion. These coalescing agents, or coalescents, facilitate the individual latex particles coming together to thereby form a continuous film at a given temperature by reducing the minimum film-forming temperature (MFFT) of the latex polymer. Thus, as used throughout, the coalescents of the invention reduce the minimum film-forming temperatures of the coating compositions in which they are used, as further described below.
Traditional coalescents are described as fugitive coalescents since they tend to escape from the coating film over time. As a result, in some jurisdictions, such coalescents are regulated as VOCs, or volatile organic compounds. A need therefore exists for a non-fugitive coalescent that is capable of meeting the VOC regulations imposed on the paint industry.
Additionally, in recent years, there has been increased interest in renewable, bio-based materials, also due to environmental concerns. It is therefore an object of the invention to provide coalescents that may be used in coating compositions that are low in VOC emissions, and that can be made from bio-based materials.
U.S. Pat. No. 7,524,896 discloses a plasticizer composition that includes a hydroxypivalyl hydroxypivalate ester and a neopentylglycol ester. The plasticizer composition is said to provide a polyvinyl chloride resin having excellent properties of heat loss, migration resistance and plasticization efficiency, and tensile strength and elongation.
There remains a need in the art for latex coating compositions having a reduced VOC content compared with those taught in the art and that exhibit satisfactory coalescing activity.